1275981661 has 2 divisors, whose sum is σ = 1275981662. Its totient is φ = 1275981660.

The previous prime is 1275981611. The next prime is 1275981671. The reversal of 1275981661 is 1661895721.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 1221502500 + 54479161 = 34950^2 + 7381^2 .

It is a cyclic number.

It is not a de Polignac number, because 1275981661 - 2⁷ = 1275981533 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (1275981611) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 637990830 + 637990831.

It is an arithmetic number, because the mean of its divisors is an integer number (637990831).

Almost surely, 2^1275981661 is an apocalyptic number.

It is an amenable number.

1275981661 is a deficient number, since it is larger than the sum of its proper divisors (1).

1275981661 is an equidigital number, since it uses as much as digits as its factorization.

1275981661 is an evil number, because the sum of its binary digits is even.

The product of its digits is 181440, while the sum is 46.

The square root of 1275981661 is about 35720.8855013422. The cubic root of 1275981661 is about 1084.6296628735.

The spelling of 1275981661 in words is "one billion, two hundred seventy-five million, nine hundred eighty-one thousand, six hundred sixty-one".